The Utility Belt has several items over the specified 0.5 kg weight (Medpac, Tool Kit, and Glow Rod). No official reason has been given as to why these items are allowed to "Outweigh" the belt. The Gamemaster may have you use any of the following fan-speculated solutions to this discrepancy or ignore it altogether:

Items over the specified weight hang off the Utility Belt and the Ration Packs are in separate pouches, leaving 3 empty pouches at purchase.

The Utility Belt has a maximum weight capacity of 5 kg, but can only have 10 different items.